The use of solid block compositions in institutional and industrial cleaning operations was pioneered in Ecolab's SOLID POWER.RTM. solids or solid detergent block technology. This technology was first claimed in Fernholz et al., U.S. Reissue Pat. Nos. 32,763 and 32,818. Further, pelletized alkaline detergent materials are shown in Gladfelter et al., U.S. Pat. Nos. 5,078,301; 5,198,198 and 5,234,615. Extruded alkaline detergent materials are disclosed in Gladfelter et al., U.S. Pat. No. 5,316,688.
In these pioneering technologies, substantial attention was focused on how the alkaline materials, based on a substantial proportion of sodium hydroxide can be cast and solidified. The first solid block products used substantial proportions of a solidifying agent, typically sodium hydroxide hydrate, to solidify the cast material in a freezing process using the low melting point of sodium hydroxide monohydrate. In the manufacture of the solid block, the particulate components of the detergent were dispersed in a liquid phase comprising aqueous sodium hydroxide and cooled for the purpose of solidifying a useful, functional solid with the dispersed compositions. The resulting solid comprises a matrix of the hydrated sodium hydroxide with the other detergent ingredients dissolved, dispersed or suspended in the hydrated matrix. In these pioneer products low melting sodium hydroxide hydrate is an ideal detergent candidate because the highly alkaline nature of the caustic material produces excellent cleaning and efficient manufacture. Another hydration type process for making cast, caustic or carbonate based detergent are disclosed in Heile et al., U.S. Pat. Nos. 4,595,520 and 4,680,134.
During the manufacture of solid block detergent compositions, we have found that condensed phosphate compositions can be hydrolytically unstable or can revert to less active phosphate species. When contacted with strong base, water and castable liquid compositions, the condensed phosphate compositions can hydrolyze and form orthophosphate or pyrophosphate compositions. The strong base and other chemical constituents of the solid block detergents can also have deleterious effects on chlorine sources, organic materials and the uniformity of dispensing. Chlorine sources are often used for destaining. Such active chlorine sources often react with compositions in the solid block and are substantially reduced in activity or concentration under harsh conditions. Organic materials such as the nonionic surfactants or defoamer compositions can react and brown, discoloring the solid. A variety of enzyme compositions can also be unstable in contact with the alkaline materials in the solid functional material. The instability can be the result of chemical incompatibility or high temperature deactivation of the enzyme protein structure. Lastly, under certain circumstances, the cast solid block material can dispense nonuniformly. By nonuniform dispensing we mean that as the aqueous spray in a spray on dispenser contacts the surface of the alkaline material within a capsule, a hemispherical eroded surface is formed. That is, the caustic material is consumed, the hemispherical surface erodes through the caustic mass until the spray reaches the bottle bottom leaving "shoulders" of the caustic material in the bottom corners of the capsule. As spray on dispensing continues, these shoulders can often crumble and result in dispenser plugging and nonuniform dispensing.
In the commercial manufacture of solid caustic materials, the hydrolysis of condensed phosphate additives can be controlled using a variety of careful process controls. Encapsulated chlorine sources have been used in solid detergents to avoid chlorine instability problems. A significant need exists to improve encapsulated chlorine source stability in solid block detergents. Further, the stability of one or more organic materials in the harsh caustic solid block environment when coming in contact with reactive chlorine sources, etc., can result in substantial instability. A need exists to increase the stability of organic materials in solid block detergents. Lastly, the improved uniformity in dispensing can improve economy in the use of solid block detergents. Accordingly, a need exists to enhance dispensing uniformity. A substantial need exists to improve the quality of the dispensing or erosion caused by the action of the water spray on the surface of the solid detergent. Further, when the capsule is nearly depleted of detergent, the nonuniform dissolution of the material can introduce an excess or minimal amount of cast solid material into the liquid concentrate which is then directed into the warewashing machine.
An extrusion technology has been developed in which condensed phosphate hydrolysis has been minimized during production by reducing the amount of water and the heat history of the composition during manufacture. Such conditions prevent hydrolysis because the materials are not substantially heated and even if heated, do not come in contact with sufficient water to produce a hydrolytic reaction condition. Such processes are shown in Olson et al., U.S. Ser. No. 08/176,541, Schultz et al., U.S. Ser. No. 08/175,626 and Schultz et al., U.S. Ser. No. 08/175,950, now abandoned.
In the manufacture of solid detergents the use of organic solidification agents is also known. Such agents include a large variety of materials including materials that solidify by cooling and hardening at a temperature below their melting point. One example of such a hardening agent is polyalkylene oxides including polyethylene oxide, polypropylene oxide and block or heteric (including random, statistical, alternating, and graft) copolymers thereof. Typically, such materials have a molecular weight greater than about 800 to 8000 and higher, do not contain vicinal hydroxyls and have not been shown in the past to contribute to hydrolytic stability of condensed phosphate materials. Representative examples of such a disclosure is shown in Morganson, U.S. Pat. No. 4,624,713 and 4,861,518.
Cristobal, U.S. Pat. No. 4,320,026 teaches using a diol compound to reduce discoloration in solid detergents.
Alternate methods of reducing hydrolytic instability of condensed phosphates have utility in areas where access to known technology is limited. Such can include small manufacturers, remote manufacturers or sites with limited processing capability. Accordingly, a substantial need exists to provide alternative solid detergent manufacturing capability with reduced condensed phosphate hydrolytic stability. Further, such alternative methods should also aid in improving stability of encapsulated chlorine sources, organic compound stability, enzyme stability and dispensing uniformity.